First, apply Vaseline around your hairline to protect your skin from stains. And make sure to wear the gloves that come in the box -- color stains hands too.

Don't start applying willy-nilly: Divide hair into four quadrants -- sideways from ear to ear, and vertically from forehead to the nape of the neck. Secure each with a clip. Work the bottle through one section at a time, then clip the hair out of the way and move on to the next section. This ensures that your entire head gets equal treatment.

Just doing roots? Coat ends with conditioner to act as a barrier, so even if color drips, it won't absorb.

For all-over color, apply to roots only for the first 20 minutes, then comb through to ends for the remaining 10 minutes -- this makes for more natural-looking results. (Don't do this if you have highlights, though -- they'll disappear entirely.)

Gray hair can be more resistant to color, so pros swear by Ardell Gray Magic Color Additive, $6. Add four to five drops to your mix and shake.